It's definately a fuel supply problem. It's not getting enough fuel so you have to choke it but the choke is not a fine enough control to make it run right.

Then, as the engine uses fuel faster than it's being supplied, it starts to run correctly for a short time, then finally dies of starvation.

Most all of the B/S engines I've worked on have an underslung fuel tank and a fuel pump of sorts that uses intake pulses to pump fuel into a pre-tank where it's used by the engine.

If this one is the same, I'd be willing to bet that the fuel pump is stuck and not functioning properly. It's housed under a plate on the side of the carb held on by about 5 screws.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250